The Present Disclosure relates, generally, to a transmission device for transmitting high-frequency waves such as millimeter waves and microwaves.
The waveguide disclosed in Japanese Patent No. 3902062, the content of which is fully incorporated in its entirety herein, is a waveguide for transmitting millimeter waves and microwaves and which is made of a dielectric material with a conductive coating. In the '062 patent, the conductive material provided on the surface of the waveguide has a slit on the bottom surface in the end portion. The end portion of the waveguide is arranged on a printed circuit board, and the slit is positioned on an electrical wire functioning as the antenna which is formed in the printed circuit board.
In the structure disclosed in the '062 patent, electromagnetic waves emitted upwards from the electrical wire pass through the slit and into the wave guide, and are transmitted through the waveguide. However, the electromagnetic waves emitted downward from the electrical wire (the electromagnetic waves emitted towards the printed circuit board) enter the waveguide with difficulty, and significant transmission loss occurs.